In sequential introduction and withdrawal designs, what is tested by adding and then removing an intervention?

• A. Long-term effects of the intervention
• B. Immediate effects of the intervention
• C. Interaction between multiple interventions
• D. Effects of the independent variable

Answer: (D)

In sequential introduction and withdrawal designs, the primary focus is on examining the effects of the independent variable, which is the intervention being introduced and removed during the study. This approach allows researchers to systematically observe how the target behavior changes in response to the presence or absence of the intervention.

By adding the intervention, researchers can analyze the immediate effects and determine how the behavior is influenced by the intervention itself. Conversely, when the intervention is withdrawn, it provides insight into whether the behavior reverts to baseline levels or remains altered. This design is particularly useful for demonstrating causality, as it highlights the direct relationship between the independent variable and the dependent variable (the behavior being measured).

Thus, the correct answer emphasizes the primary goal of assessing how the independent variable—represented by the intervention—affects behavioral outcomes over time, through both its introduction and subsequent withdrawal.